This invention relates generally to fasteners cumulatively binding flexible sheets together in a stack, and more particularly to a sheet fastener hinge device to removably hinge a second stack of sheets to a first stack of sheets.
Most office files have thin metal sheet fasteners with a pair of manually bendable prongs extending from an elongated base to cumulatively bind the sheets paper together in a stack. The prongs extend through matching pairs of aligned apertures adjacent one edge of the sheets and outer portions of the prongs are bent over the stacked sheets to securely bind them together adjacent that edge. This allows part of the stack to be lifted up and bent back to see any one of the sheets of paper in the stack. Also, one or more sheets can easily be added to or removed from the stack by first straightening out the outer portions of the prongs and then adding or removing the sheet or sheets. In some cases, an elongated retaining or compressor bar having slidable cross bands is mounted between the prongs on the front of the stack of sheets to more securely retain the bent prongs in place. In some instances, the fastener also extends through a pair of apertures in a file cover to secure the stack of papers to the file cover.
While these existing fasteners are satisfactory for many applications, they have the disadvantage that only a limited number of sheets can be bound in one stack. When the thickness of the cumulative stack of sheets approaches the length of the prongs, the outer portions of the prongs left extending from the stack are not long enough to be bent over to hold the sheets together. Furthermore, when the stack becomes this thick, access to sheets of paper near the rear of the stack becomes quite difficult. Also, it is very inconvenient to add or replace a sheet of paper near the back of the stack as all of the sheets in front of it have to be removed and then replaced.
A device for fastening two stacks of sheets of paper on opposite sides of the spine of a file :folder disclosed in U.S. Pat. No. 1,987,012 to Karlen which issued Jan. 8, 1935. Another attempt to overcome these problems by using interlocking paper fasteners is shown in U.S. Pat. No. 2,571,044 to Lynch which issued Oct. 9, 1951. However, access to the sheets near the back of a thick stack is still very poor. U.S. Pat. No. 2,352,196 to Hartmann which issued Jun. 27, 1944 does show a hinged blank holding a pronged fastener, but it is for securing a single group or stack of sheets in a file folder.